Impact of sodium dodecylbenzene sulfonate (SDBS) On some soil biological indices

The aim of this study was to assess the impact of SDBS on some biological indices including microbial respiration, microbial biomass carbon, nitrogen and phosphorus, microbial quotient and metabolic quotient in a soil from Osku area. The experiment was conducted as repeated measures with between-subjects factor of SDBS at four levels of 0, 0.01, 0.05 and 0.25% and within-subjects variable of time intervals at six levels of 2, 7, 15, 30, 60 and 90 days with three replications. Based on results, all biological indices declined (except for metabolic quotient which increased) in comparison with the control after application of SDBS. Soil microbial respiration decreased over time in each level of SDBS and the corresponding values were significantly lower at 0.01 and 0.05% of SDBS than those at zero and 0.25% of SDBS. This trend was also observed for soil microbial biomass carbon. Being soil microbial community under stress at 0.01 and 0.05% of SDBS and induction of tolerance at 0.25% of SDBS could explain these results. Soil microbial biomass nitrogen on the second day of incubation increased with increasing the SDBS level and decreased over time in all levels of SDBS (expect for control). Increasing microbial nitrogen biomass in the SDBS treated soils might be due to increasing the activity of Azotobacters or other nitrogen-fixing bacteria which are less sensitive to SDBS and are able to feed through it. The highest values of microbial biomass phosphorus were recorded in SDBS treated soils on the second day of incubation, but the values severely decreased after one week and thereafter the changes were negligible.